If the person tells you it's ok for you to touch them, it's fine, but don't rush it.

Pay attention. If the person tries to reach you, be there. If the person tries to tell you to not look : don't look. Be there. It might seem stupid but trust me, it isn't at all.

If the person is afraid of something, ask what. Try to do something about it. In my case I become extremely afraid of direct lights, even the ones far away. I become afraid of sounds, sometimes of open doors, sometimes of closed doors, sometimes of walls, etc.

It isn't rational. But if you can help, ask and try. Don't do things without asking or listening closely first.